Electrolyte replacement
Potassium mEq/L Goal -''' correct to 4.0 'Etiologies -' vomiting, diarrhea, NGT, diuresis, alkalosis, low magnesium, hyperaldosteronism, RTA, increased insulin, increased beta-adrenergic activity, hypokalemic periodic paralysis, amphotericin, salt-wasting nephropathies (including Liddle's, Barter and Gitelmann syndromes) '''Symptoms of hypokalemia: * muscle weakness (progresses lower to upper extremities) or cramps and rhabdomyolysis (can involve resp muscles or GI muscles with ileus), * arrhythmias (U waves, prolonged QT interval, PAC/PVCs, bradycardia, AV block, Vtach/Vfib) General Principles: * 10mEq raises serum potassium by 0.1 * Give oral if can tolerate and not severe. Give oral dose of max 20mEq (60mEq per VA) q2hr until repleted. Drink with lots of water to prevent GI irritation. * If replacing by IV, recommend 10mEq/hr replacement (with peripheral line. may go up to 20 mEq/hr with central line - and even 40mEq/hr if emergency, but put on tele). * Also, max concentration of 5mEq/50ml if using a peripheral line, and 20 mEq/50mL if using a central line - try doing half that if possible. * recheck 2 hrs after an infusion, 4 hours after oral replacement Oral replacement IV replacement Magnesium mg/dL Goal -''' correct to 2.0 'Etiologies -' diarrhea, PPIs, malabsorption/steatorrhea, acute pancreatitis, diuretics (loops, thiazides), antibiotics (aminoglycoside, amphotericin), alcoholism, hypercalcemia, renal tubular dysfunction (ATN recovery, postobstructive diuresis, post-renal transplant), uncontrolled diabetes '''Symptoms of hypomagnesemia: * neuromuscular hyperexcitability (tetany - Trousseau and Chvostek signs, spasms, cramps) * hypocalcemia (from hypoparathyroidism, PTH resistance and vitamin D deficiency) * arrhythmias (widened QRS, peaked T waves, prolonged PR interval, torsades and ventricular arrhythmias) * seizures * involuntary movements (athetoid or choreiform) * if severe, apathy, delirium, coma, vertical nystagmus General Principles: * serum magnesium is poor reflection of repletional status as most magnesium is intracellular * 1mmol=2mEq=24mg elemental magnesium = 240mg magnesium sulfate/200mg MgCl * typical daily PO dose if normal renal function is 240-1000mg elemental magnesium (20-80 mEq/10-40mmol) in divided doses. All PO repletion has limited bioavailability. * Don't infuse faster than 1g q30min (unless life-threatening, can give 2g IVP in code). Standard IV concentrations are 1g/100ml or 2g/50ml. * recheck magnesium 2 hrs after infusion * slow infusions will allow for greater retention of magnesium * IM can be very painful and has no therapeutic advantage over IV Oral replacement IV replacement Phosphorus mg/dL Goal -''' Stop repletion when >= 2.0mg/dL. If CKD, maintain 2.7-4.6 mg/dl (0.87-1.49mmol//L). In ESRD, maintain 3.5-5.5 mg/dL (1.13-1.78 mmol/L) 'Etiologies -' increased glycolysis (insulin, glucose, glucagon, epinephrine, acute respiratory alkalosis, hungry bone syndrome after thyroidectomy/parathyroidectomy), poor intake, diarrhea, prolonged antacids or phosphate binders, increased urinary excretion (hyperparathyroidism, vit D deficiency, Fanconi syndrome), dialysis, renal transplant '''Symptoms of hypophosphatemia: * mineral metabolism - decreased distal tubule reabsorption of calcium and magnesium, inceased bone resorption, hypercalciuria, rickets and osteomalacia if prolonged * ATP depletion - metabolic encephalopathy, impaired myocardial contractility, respiratory failure to diaphragm weakness, proximal myopathy, dysphagia, ileus * if acute, can cause rhabdomyolyis * predisposed to hemolysis, thrombocytopenia General Principles: * Replete orally if <2.0mg/dL and asymptomatic * Treat with oral repletion if 1.0-1.9mg/dl and IV repletion if <1.0mg/dL (then switch to oral once >1.5). If CKD, start with 50% suggested initial dose. Many different oral formulations exist with varying levels of Na and K - double check to make sure what you are giving. * If oral and phosphate >1.5, give 1 mmol/kg elemental phosphorus TID-QID (give 40-80 mmol/day) * If oral and phosphate <1.5, give 1.3-1.4mmol/kg elemental phosphorus TID-QID (max 100 mmol/day) * IV therapy is dangerous because it can precipitate with calcium (causing hypocalcemia, renal failure due to precipitation, fatal arrhythmias) * IV therapy based on severity of hypophosphatemia and weight of pt. Monitor q6hrs/2hrs after infusion complete. May give doses up to 1mmol/kg for severe. * use adjusted body weight in pts >130% IBW Oral replacement IV replacement Calcium mg/dL Goal -''' Correct underlying causes. Ionized calcium mg/dL 'Etiologies -' hypoparathyroidism (postsurgical, autoimmune, hungry bone syn, HIV), PTH resistance, vitamin D deficiency, low magnesium, inhibitors of bone resoprtion (meds), renal dz, loss of calcium from circulation (hyperphosphatemia, tumor lysis, acute pancreatitis, osteoblastic metastases, acute respiratory alkalosis, sepsis or severe illness) '''Symptoms of hypocalcemia: * neuromuscular irritability - paresthesias, spasm, tetany (Trousseau and Chvostek sign) * hypotension, decreased cardiac function (even CHF), prolonged QT interval * seizures * papilledema when severe * AMS, emotional instability, anxiety, depression, hallucinations General Principles: * check albumin, and for ionized calcium * corrected Ca = Ca + 0.8 * (4-albumin) * don't infuse IV calcium and IV phosphate-containing solutions in the same line * Max IV infusion rate = 1.5mEq/min * For PO replacement of mild/mod, asymptomatic hypocalcemia, supplement with 1-3g elemental calcium Oral replacement IV replacement Category:Medicine